Valve arrangement for steam-engines



NTED STATES PATENT OFFICE.

NAHUM S. C. PERKINS, OF NORWALK, OHIO.

VALVE ARRANGEMENT FOR STEAM-ENGINES.

Specification of Letters Patent No. 19,098, dated January 12, 1858.

To all whom 'it may concern:

Be it known that I, NAHUM S. C. PERKINS, of Norwalk, in the county ofHuron and State of Ohio, have invented a certain new and usefulImprovement in Duplex Valve Arrangements of Steam and other Engines, ofwhich the following is a full, clear, and exact description, referencebeing had to the accompanying drawing, which forms part of thisspecification, and in which- Figure l represents a partly sectional sideelevation of a horizontal reciprocating steam engine with my improvementapplied thereto, said view being taken mainly as indicated by theirregular line, a: m, in Fig. 2, which latter figure represents a topview or plan of the engine with the valve chest cover removed andshowing a cylinder situated within said chest in section. Fig. 3representsa transverse vertical section of the main engine cylinder andsteam chest with its interior cylinder, taken mainly as denoted by theline, a z, in Fig. 2, but omitting representation of the valves andother operating parts, and Fig. 4 represents a side elevation of theengine, with certain of the interior operating parts, in colored anddotted lines, in posi tions the reverse of those shown for the sameparts in Figs. l and 2.

Like letters of reference indicate like parts throughout the severalfigures;

My improvement has reference to that class of valve arrangements forreciproca-ting piston engines, in which, a main valve is made to openand close, in proper order to keep up a reciprocating action of theengine piston, the several inlet and exhaust ports to the main cylinderof the engine, thro-ugh pressure of the propelling Huid brought to bearon and operate said main valve abruptly, at or shortly before the closeof the engine piston stroke only, by means of a secondar or lap valvearranged to control the admission and escape of the propelling fluid tooperate the main valve, said controlling valve being driven by theengine. These valves, for operation together as described, I preper toarrange in a steam chest common to them both and make one exhaust outletserve for both, as has before been done in duplex valve arrangements ofthe character here referred to, and my improvement is designed moreparticularly to apply to direct acting engines of the reciprocating kindsuch as usually employed for driving pumps and saw mills by the directconnection of the driven machinery with the piston rod of the engine andwithout the intervention of a .crank or rotary movement.

The engine represented in the accompanying drawing is shown in ahorizontal position or as adapted for horizontal action. Its maincylinder (A) is provided with the usual end lids or covers (a a), glandsor stuling boxes (b b), and a steam chest (B) on its top having steamsupplied it by a pipe (B). The main or engine piston (C) has its rod (c)arranged to protrude through eitherend of the cylinder, though this neednot, necessarily, be so.

Rigidly attached to the main piston rod (c), at or near its one end say,is an ordinary cross-head or block (D), that, during the reciprocatingtravel of the piston, slides along a fixed guide (E) fast to the maincylinder. The cross head (D), thus reciprocating with the piston, ismade to give a uniform or constant swinging action, by means of a linkrod (d), to a lever (F), whose fulcrum (c), is intermediate of thelength of the lever on the fixed giude (E) the longer arm of said leverbeing driven by the crosshead, and the shorter arm of it serving toreciprocate, by the interposition of rods (f f), a lap valve (G). Thislap valve (G) is situated within the steam chest (B), has an exhaustcavity (g), and is arranged to reciprocate over or along a small steamcylinder (H) ixed within the steam chest, so as to admit steam andexhaust it alternately to and from either side of a piston (I) arrangedWithin said small cylinder which latter has a steam passage (L h), neareither, communicating with the steam space of the chest, and a centralexhaust passage (i) communicating with the general exhaust outlet (J),as shown in Figs. 2 and 3 of the drawing. The lap valve (G) plays overthe several passages, (laJ h and to give a reciprocating action to thesmall piston (I), and is so pitched as regards lap .and stroke as tomake this action to said small piston an intermittent one and cause itonly to be moved shortly before the engine piston (C) reaches the end ofits stroke or single movement in either direction. This small piston (I)has a rod (7c) that passes out through either end of the small cylinder(H). This rod (7c) is also the stem or rod to the main valve or valves(K K), which slide on or over seats (L L) that have passages (Z Z)communicating, by other passages m), with either end of the main steamcylinder (A), and have further passages (Z2 Z3) communicating withbranch passages (n n) that form a connection with the main cylinder, onthe opposite side of the engine piston, to the steam in the chest (B).The stroke of the main valves (K K) and their piston is preferably madeadjustable and limited to vary the area of the passage surface uncoveredfor the admission of steam to the engine cylinder according to the slowor rapid motion of the engine, by extending the main valve stem (Z6)through the steam chest and through screw boxes or stops (r r) whichwork through bosses (s) of a standard (S) fast to the steam chest. Thesescrew boxes freely turn on the valve stem (Z0), and, accordingly as theyare brought nearer or farther apart by screwing or unscrewing them in orout of the bosses (s), is the stroke of the valves (K K) made shorter orlonger so as to open more or less the one or both inlet ports (Z Z) ofthe engine when said valves are thrown; by a stop or boss (u) on thevalve stem (7e) coming sooner or later into contact with the screw boxes(1' r).

Supposing the several parts to be in the position shown in Figs. l and 2of the drawing, which figures show a like position of the same parts,the main engine piston (C), it will be seen, is at the end of itsforward stroke or in position of starting back on its return stroke,while the small piston (I) has been driven backward, by the lap valve(G) opening the one steam inlet (Zz) of the small cylinder (H), whichback movement of the small piston (I) has, by connection of said pistonwith the main valves, operated said main valves (K K) so as to givesteam 'in front of the engine piston (C) through the passages (Z m), andpass off the steam at the back of the engine piston through the passages(m, Z), valve cavity (0) and exhaust passages (Z3 n), to the exhaustoutlet (J). But upon the engine piston (C) reaching the extremity of itsback stroke, or rather shortly previous thereto, as represented in Fig.4L of the drawing, the lap valve (G), by the action of the lever (F),will have ope-ned the opposite steam inlet L) of the small cylinder andthereby have caused the small piston (I) to be driven forward and theposition of the main valves (K K) to be changed so as to admit steam atback of the engine piston (C) through the passage (Z m), and pass offthe steam in front of the engine piston through the passages (m, Z),valve cavity (o), and exhaust passages (Z2 n), to the exhaust outlet (JThe lap valve (G) alternately exhausts the small cylinder (H) on eitherside of its piston (I), by its exhaust cavity (g) alternately connectingthe small cylinder ports (h h) with the central exhaust passage thatconnects with the main outlet (J), and the arrangement shown in thedrawing, it will be observed, is such, that the lap valve exhausts thesmall cylinder` on the one side ot its piston (I), before it admitssteam on the opposite side of said piston to move the main valves, so asto insure a rapid and easy movement of the main valves, and secure thegeneral exhaust outlet (J) being clear before the steam from the maincylinder is passed to it. In this way is a continuous reciprocatingaction kept up of the engine piston (C). The lap valve driving lever (Fbeing in permanent gear with the engine piston so as to have a constantmotion during the entire travel of the piston and said auxiliary valveconnection being a continuously operating one with or from the enginepiston direct, all such destructive shock, jar, jerk or concussion as isproduced by a lever or tappet struck by a moving portion of the engineto operate t-he valve is as perfectly avoided as if the-auxiliary valve(G) were driven by the ordinary eccentric gear ofv an engine having arotary motion, in comparison with which, apart from the greatercompactness and simplicity of the one inode of action over the other,any sudden variation of velocity on part of the engine piston at, say,toward the close of the stroke, is, in the present arrangement moreimmediately felt by the lap valve (G) to govern its controlling actionover the abruptly operating main valves (K K), an important feature induplex valve arrangements of the description here referred to, in which,it is a main obj ect to open and close the engine ports abruptly atcertain points, only, relative to the engine pistons travel, incontradistinction to a slow or gradual opening and closing of them as byan ordinary slide valve receiving its motion direct or otherwise in aconstant, or regular manner, to open and close the engine ports direct;and which abrupt action of the main valves (K K) at or shortly beforethe close of the engine piston stroke only, is here, by the constructionand arrangement of parts as before described, effected in a most perfectand smooth manner and without presentation of irregular resistance onthe part of the devices connected with the operating portions of theengine for eifecting said abrupt or.

occasional movement ofthe main valve or valves, and the arrangement as awhole 1s one that, for its dlrect and smooth operation,

valve (G) permanently linked or geared thereto for like continuousoperation, and L5 independent, intermittent, piston or pressure drivenmain valve or valves (K K), for operation together relatively to eachother and the engine piston as specified.

In testimony whereof, I have hereunto 2O subscribed my name.

NAHUM S. C. PERKINS.

Witnesses:

CHAS. P. WICKHAM, ED A. BUTTS.

